Oh boy,, you've touched a nerve for the San Francisco residents! Thousands of people go about their daily lives without giving this a thought. But seismologists predict that the Hayward Fault Line is due 'for a lurch'.. that could set off a tremblor in the Bay Area. In such an event, homeowners should know how to turn off the main gas valve. Depending on the intensity of the shake, there could be extensive damage. In terms of preventative action, they are advised to add reinforcements, bolting the home to the foundation. Beyond that, there should be an emergency kit and plan of action. If you're worried about earthquakes, this might not be where you want to be!